Objectives of the project are: 1) Elucidate the relationships between peptide structure and metal-binding activity of synthetic oligopeptides which contain three cysteine residues; and 2) examine the detoxification effects of the metal-binding peptides against Cd and Hg in animals. A naturally existing protein designated as thionein obtained from various mammals has strong metal-binding activity, and the protein has been implicated in detoxification of harmful metal ions. Thionein consists of about 60 amino acid residues, among them 20 are cysteine. One molecule of thionein binds to about 7 metal ions, indicating that three -SH groups are involved in mercaptide formation. We synthesized several oligopeptides (6-13 amino acid residues) which contained three cysteine residues, and found that the synthetic peptides also had strong metal-binding activity. In the proposed project, various peptides which contain three cysteine residues, will be synthesized by the solid-phase method and liquid-phase method. The peptide will be purified by ion-exchange chromatography and reverse-phase chromatography. Binding activity of the peptides towards Cd, Hg and Zn will be determined. The peptides with strong affinity to Cd and Hg will be used for detoxification of animals which have been treated with these harmful metals.